I'm designing an active LIPO balancer for a hybrid power system that recharges from a gas generator, so it needs to be a lot different from a passive/resistor type balancer you'd have on a normal battery charger. For starters, my battery pack (a 12Sx3.3volt battery built from A123 26650 cells - 39.6 total stack voltage) will never (not from the generator anyway) be allowed to charge above more than about 70 percent SOC, and never allowed to drain below about 40 percent SOC before the charging generator comes back on.
Obviously I need the ability to actively and precisely balance the voltages during heavy discharge and charging both, and I'll never (or rarely) get the opportunity to do a top or bottom balance like normal chargers do. It's worth it to me to spend good money on the best and most efficient design I can do on this balancer so as to lower the fuel consumption of the generator engine.
My current design I'm drawing right now, is based on two chips from Linear Technology. The first is the LTC 3300-1 balancer controller, which uses external MOSFETS and tiny flyback transformers to send current bidirectionally between individual cells and a stack of six. I'll need two of these to do a 12S stack of batteries. The second chip is the LTC 6804-1 which is a battery voltage monitor that integrates with the LTC 3300-1.chip. The LTC 6804-1 has the ability to do passive balancing through resistors and external MOSFETS, but I do not plan to use this, and will only do active balancing through the LTC 3300-1's, and only use the 6804-1 to get super accurate voltage and temperature measurements. I like this setup because it allows me to use tiny, off-the-shelf flyback transformers I can buy for about 3 bucks each, instead of having to make a custom transformer(s).
I will have to connect my own micro-controller to this setup and provide my own software to control it, which will be written especially for the charging needs (staying between 40-70 percent SOC) of a series gas/hybrid charging system. Charging above about 70 percent is too wasteful with gas. I'm super concerned with being as efficient as possible about turning gasoline into stored electricity here not because of the cost of the fuel, but because of it's WEIGHT. This is an aircraft application, so making my charger a lot more expensive is not a problem if it lowers the weight of the fuel I need to carry.
Now that you know the story, my question is this:
Do other companies besides Linear Technology make controller chips similar to what I'm already planning to use, or do these two represent the current state of the art in actve LIPO balancer design? Is there some other better idea than using flyback transformers to build an active LIPO balancer? I'm interested in taking a sort of survey on what's available so I can compare features. If anyone makes a single chip that does the functions of both the LTC 3300-1 and the LTC 6804-1, I'd really like to hear about it.
Even a suggestion about what words to do a Google search for would be appreciated.
Thanks an advance for any help.
Meadows.
Obviously I need the ability to actively and precisely balance the voltages during heavy discharge and charging both, and I'll never (or rarely) get the opportunity to do a top or bottom balance like normal chargers do. It's worth it to me to spend good money on the best and most efficient design I can do on this balancer so as to lower the fuel consumption of the generator engine.
My current design I'm drawing right now, is based on two chips from Linear Technology. The first is the LTC 3300-1 balancer controller, which uses external MOSFETS and tiny flyback transformers to send current bidirectionally between individual cells and a stack of six. I'll need two of these to do a 12S stack of batteries. The second chip is the LTC 6804-1 which is a battery voltage monitor that integrates with the LTC 3300-1.chip. The LTC 6804-1 has the ability to do passive balancing through resistors and external MOSFETS, but I do not plan to use this, and will only do active balancing through the LTC 3300-1's, and only use the 6804-1 to get super accurate voltage and temperature measurements. I like this setup because it allows me to use tiny, off-the-shelf flyback transformers I can buy for about 3 bucks each, instead of having to make a custom transformer(s).
I will have to connect my own micro-controller to this setup and provide my own software to control it, which will be written especially for the charging needs (staying between 40-70 percent SOC) of a series gas/hybrid charging system. Charging above about 70 percent is too wasteful with gas. I'm super concerned with being as efficient as possible about turning gasoline into stored electricity here not because of the cost of the fuel, but because of it's WEIGHT. This is an aircraft application, so making my charger a lot more expensive is not a problem if it lowers the weight of the fuel I need to carry.
Now that you know the story, my question is this:
Do other companies besides Linear Technology make controller chips similar to what I'm already planning to use, or do these two represent the current state of the art in actve LIPO balancer design? Is there some other better idea than using flyback transformers to build an active LIPO balancer? I'm interested in taking a sort of survey on what's available so I can compare features. If anyone makes a single chip that does the functions of both the LTC 3300-1 and the LTC 6804-1, I'd really like to hear about it.
Even a suggestion about what words to do a Google search for would be appreciated.
Thanks an advance for any help.
Meadows.
